Stems for electrical devices



Jan. 16, 1962 D. T. ZARBOCK 3,017,451

STEMS FOR ELECTRICAL DEVICES Filed Dec. 29, 1959 lnven tov: Donabd T. Zarbock His A t tro neg United States Patent 3,017,451 STEMS FOR ELECTRICAL DEVICES Donald T. Zarbock, Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Filed Dec. 29, 1959, Ser. No. 862,638 Claims. (Cl. 174-5057) with an exhaust tube extending perpendicular to the press. .Lead-in wires are embedded in the press in a circle, and

the periphery of the press is sealed by fusion to the envelope, the internal assembly of filament and/or electrodes being supported within the envelope on the lead-in wires.

Difliculties have been encountered during the sealing of such stems to the envelopes.

When the body of the disc press is made relatively thick for rigidity and strength, and is provided with a relatively thin edge for sealing to the envelope, severe strains may be set up in the press, resulting in cracks. When the press is made relatively thin, it is subject to warping or sagging with resulting misalignment of theparts.

It is therefore an object of my invention to provide an improved stern of the type described and which is resistant to warping or sagging during the sealing-in process, and which is capable of assuming a desirable strain pattern such that it is resistant to cracking. It is another object to provide such a structure which is simple and inexpensive to manufacture.

The novel features of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a perspective view of a stem of the type comprising my invention;

FIG. 2 is a plan view of the bottom of the stern;

FIG. 3 is an elevation, in section, of the stem taken along the line 3-3 in FIG. 2; and

FIG. 4 is an elevation, in section, of a form of incandescent lamp embodying a stem made in accordance with the invention.

Referring to the drawing, the stemcomprises a relatively thin, fla-t, glass disc press portion and a plurality (four) of lead-in wires 11 extending through the press and having portions thereof hermetically sealed in the press. The said lead-in wires are arranged in a circle within the periphery of the press. Preferably, inner and outer bosses 12 and 13 (FIG. 3) are formed around the lead-in wires at opposite sides of the press to increase the length and strength of the seal. While the lead-in wires 11 may each consist of a continuous length of wire of an alloy having a coefficient of expansion matching that of the glass, they preferably are of the composite, threepiece type including a short intermediate length 14 (FIG. 3) of conventional Dumet wire (a nickel-iron core with a copper sleeve), an outer lead portion 15 preferably of nickel, and an inner lead portion 16 preferably of nickeliron alloy.

As illustrated herein, the press 10 has a central exhaust opening or hole 17 communicating with a glass exhaust tube 18 which extends perpendicularly from the press. Also, the outer or bottom surface of the press is provided 3,017,451 Patented Jan. 16, 1962 with a plurality (four) of locating bosses 19 spaced apart between the lead wires 11 and located in the same circle as said lead wires. The bosses 19 define a plane for accurate location of a base as hereinafter explained. Although the press 10 is already relatively thin, it is further preferred that the periphery thereof be undercut at the outer or under surface thereof as shown at 20 in FIG. 3, and that it be tapered at its inner or upper surface as shown at 21, whereby the periphery or edge of the disc press is made somewhat thinner to further facilitate sealing to the enclosing bulb or envelope.

In FIG. 4 of the drawing the press 10 is shown incorporated in an electric incandescent projection lamp wherein the press is sealed to the neck of a glass envelope 22, and its exhaust tube is tipped off at 23 to hermetically seal the envelope with a filling therein of inert gas such as nitrogen. The envelope 22 contains a tungsten filament 24 of the biplane type which is connected at its ends to conductive spuds 25 which are, in turn, connected to conductive supports 26 which are supported from a diametrically opposed pair of the lead-in wires 11, each of which is, in turn, electrically connected to a respective one of the remaining pair of lead-in wires by a cross spud 27 (only one being shown). The endsof the coiled wire segments comprising the filament 24 are supported from respective glass bridge members 28 by respective groups of insulated support wires 29. g

The lamp is also provided with a base 30 which comprises a shell portion 31 which is cemented to the neck of the bulb 22, and a central-tubular extension 32 which encloses the tip 23 of the exhaust tube and extends downwardly from the bottom or web portion 33 of the base. The base is accurately aligned and spaced from the filament 24 by engagement of its web portion 33 with the surfaces of the locating bosses 19, the said filament having been previously mounted in accurately predetermined relationship to the surfaces of said bosses 19. Thereby, during use of the lamp, when the base 30 is inserted into its socket, the filament 24 is accurately located with respect to the socket and associated equipment such as a reflector or lens.

As thus far described, the stem is of conventional construction, and difiiculties have been encountered in warping or sagging of the press 10 between the relatively widely spaced lead wires, with consequent misalignment of the locating bosses 19 and corresponding misalignment of the base 30.

During manufacture of the stem, and immediately after molding the press portion 10 to the shape shown in FIG. 1 and while it is still at a temperature above its strain point, a jet of compressed air is directed against the upper surface of the press near the center thereof and is maintained while the glass cools through the strain point. Thereby, a desirable strain pattern is formed, wherein the central portion of the press, Within the circle of the lead wires 11, is under tension, the outer periphery or edge of the press is under compression strain, and the circle of the leads is neutral. If it is attempted to provide rigidity by making the entire central portion of the press 10 thicker, with a thin edge, the strain pattern is interferred with in a manner which tends to make it very difficult to avoid cracking of the press during the sealing thereof to the bulb 22. On the other hand, careful control of the manufacturing operation, including regulation of heating and sealing flames also failed to solve the problem.

In accordance with the present invention, I have found that adequate rigidity is imparted to the press 10 without adverse effect on the strain pattern, by retaining the relative thinness of the press and adding thereto an annular stiffening ridge or rib 35 located in the same circle as the lead-in wires 11. The said rib 35 is formed during the molding of the press 10.- Upon cooling of the glass, the

press retains the desirable strain pattern described above so that, during sealing to the bulb 22, cracking is avoided and, at the same time, the press retains its shape so that misalignment of the locating bosses 19 is avoided. The said rib 35 also resists sagging of the press during the course of its manufacture.

In one embodiment of the invention, I have obtained good results with a press 10 of conventional lead glass having a diameter slightly greater than one inch and a thickness, in the central portion, of about .090 inch, the lead wires 11 being in a circle of about A inch diameter. The annular rib 35 was of cylindrical section, preferably slightly less than hemispherical for ease of withdrawal of the mold, and having a height of about .025 inch. Such a structure has successfully withstood substantial warping .or sagging in spite of the relatively large gaps between the supporting lead-in wires 11 which are preferably four in number but which may number three or even two.

It will be observed in FIG. 4 that the edge or periphery of the disc press is turned up in forming the joint with the bulb 22; this occurs during the conventional step of stretching the seal to work and consolidate the joint. The rib 35 should not be so large in width as to interfere with or touch that joint in such manner as to leave or produce a sharp angle between the surfaces at the inside of the joint such as would lead to the development of a crack in the joint. If additional stiffening or stabilization is needed, a

second similar rib may be employed on the outer or under surface of the press 10 opposite the rib 35 on the inner surface. In that event, such second rib replaces the locating bosses 19 and itself serves as the locating surface for the web portion 33 of the base.

lead-in wires spaced apart in a circle in a neutral portion between said central portion and said peripheral portion and hermetically sealed therein, said press having an integral annular rib on a surface thereof and in the same said circle as the lead-in wires so as to not disturb the tension and compression strains and serving to resist distortion of the press during subsequent fusion of an envelope to the periphery of the press.

2. Astem for an electrical device comprising a flat glass disc press havinga central portion under tension and a peripheral portion under compression, a central opening in said central portion, an exhaust tube projecting from one side of said press and communicating with said opening, a plurality of lead-in wires spaced apart in a circle in a neutral portion between said central portion and said peripheral portion and hermetically sealed therein, said press having an integral annular rib on the surface thereof opposite to that from which said exhaust tube projects 4 and in the same said circle as the lead-in wires so as to not disturb the tension and compression strains and serving to resist distortion of the press during subsequent fusion of an envelope to the periphery of the press.

3. A stern for an electrical device comprising a flat glass disc press having a central portion under tension and a peripheral portion under compression, a plurality of lead-in wires spaced apart in a circle in a neutral portion between said central portion and said peripheral portion and hermetically sealed therein, said press having an integral annular rib on a surface thereof and in the same said circle as the lead-in wires so as to not disturb the tension and compression strains and serving to resist distortion of the press during subsequent fusion of an envelope to the periphery of the press, said press further having a plurality of locating bosses in the spaces between said leadin wires and on the opposite surface of said press from said annular rib and located in the same said circle as the leadin wires. p

4. A stem for an electrical device comprising a flat glass disc press having a central portion under tension and a peripheral portion under compression, a plurality 10f lead-in wires spaced apart in a circle in a neutral portion between said central portion and said peripheral POT. tion and hermetically sealed therein with bosses formed onopposite sides of said press around said lead-in wires,

said press having an integral annular rib on a surface thereof between said bosses and in the same said circle as the lead-in wires so as to not disturb the tension and compression strains and Serving to resist distortion of the press during subsequent fusion of an envelope to the periphery of the press.

7 5. A stem for an electrical device comprising a thin flat glass disc press having a central portion under tension, a peripheral portion under compression and an interme diate neutral portion therebetween, a plurality of'lead-in wires spaced apart in a circle within said intermediate portion and hermetically sealed therein with bosses formed .on opposite sides of said press around said lead-in wires, said press having an integral annular rib on a surface there of between said bosses and in the same said circle as the lead-in wires so as to not disturb the tension and compression strains and serving to resist distortion of the press during subsequent fusion of an envelope to the periphery of the press, said press further being provided with a peripheral undercut on one of said surfaces and a peripheral taper on the other of said surfaces.

' References Cited in the tile of this patent UNITED STATES PATENTS 2,190,788 Horn Feb. 20, 1940 2,278,392 Murphy Mar. 31, 1942 FOREIGN PATENTS 571,516 Great Britain Aug. 28, 1945 

